An owlbear's screech echoes through dark valleys and
benighted forests, piercing the quiet night to announce
the death of its prey.
The 4e owlbear has an encounter power called 'Stunning Screech', and it's upgraded cold-themed variant has a 'Frost Wail'.
No information appears to be present regarding sounds from owlbears in 3.0 or 3.5.
The 'Ecology of the Owlbear' article in Dragon #214 details quite a bit about the beasts, including a short story with a bunch of different owlbear screeches in a combat, as well as an explanation that owlbears can communicate via an entire language of screeches, and stats for the gregarious-yet-no-less-murderous winged owlbears. A sample:
The screech was incredible. Colin covered his ears with both hands, amazed at the sheer intensity of the creature’s death throes. After what seemed an eternity, but was probably closer to a few scarce minutes, the owlbear dropped to its side, dead.
None of the earlier versions of the owlbear seem to list a definite sound, and most lack any sort of extensive description. The rules cyclopedia elaborates a bit on the bear hug, but the rest of the sources seem to merely update the stats for the new edition and stick with Gygax's original description in supplement I: Greyhawk, minus the Gygaxian prose (e.g. using 'head' instead of 'cranial region')
OWL BEARS: Creatures of horrid visage and disposition. Owl Bears will attack whatever they see and fight to the death. They deliver a "hug" just as a Werebear, for example, as well as great damage from beak, tooth, and claw. A large male will stand 8' tall, weigh 1,500 pounds, and have claws over 2" long. Bodies are furry, tending towards feathers over the cranial region, and the skin is very thick.
That said, among players of D&D there's been a persistent tradition of combining the hoot or screech of an owl with the roar of a bear as the noise of an owlbear, such as demonstrated in this Penny Arcade D&D game, or this homebrew sound effect for Lost Mine of Phandelever, among others.
For third edition material, it should be noted that Pathfinder does have some descriptions of owlbears and their noises and/or lack thereof, but I'm not sure that system is within the scope of your question, since it's not part of Paizo's work as the erstwhile licenced third-party publisher of Dungeon and Dragon but rather part of their standalone system in which they are the first-party author. In case you care, in Pathfinder, The First Owlbear is 'spookily silent'.